Dark Matter Halos of the Most Massive Galaxies

杰里米·D·墨菲博士被授予美国国家科学基金会天文学和天体物理学博士后奖学金，在普林斯顿大学开展研究和教育项目。目前的宇宙学范式包括一种重要的、未知的物理实体，称为“暗物质”。虽然暗物质(DM)在星系中的存在已经得到了很好的证实，但暗物质晕的范围以及暗物质在星系形成和演化中所起的作用在很大程度上是未知的。由于目前支配DM晕等级聚集的宇宙学范式对它们的形成时间尺度和合并历史做出了具体的预测，因此需要清楚地了解DM晕在星系尺度上的质量。在这个项目中，这位研究员将专注于直接限制椭圆星系形成的机制和时间尺度。最近发现的静止的红色椭圆星系在Z~2附近红移，这引发了许多关于星系形成的Lambda冷暗物质等级图的问题。幸运的是，星系为它们的形成历史留下了化学和运动学的线索。积分场光谱和动力学模拟的进展已经开始打开了解椭圆星系的Dm分布、Dm中心密度、恒星轨道各向异性和化学丰度梯度的窗口。在这个项目中，这位研究员将继续他对大质量椭圆星系形成和演化的研究。具体地说，本项目有以下目标：(1)该项目将使用来自Virus-P的2D恒星运动学和基于轨道的轴对称动力学模型来约束DM晕质量、DM中心密度、恒星轨道各向异性和恒星丰度梯度。由此，他将能够对星系形成的时间尺度和可能的机制施加直接的限制。(2)该研究员将把基于恒星运动学的质量估计与其他估计星系质量的方法进行比较，以便量化这些不同方法之间的任何系统学。(3)这位研究员将带来他在调试病毒P光谱仪方面的经验，以及他对该仪器光纤的详细研究，以便成功地在拉斯坎帕纳斯天文台的杜邦望远镜上安装一台复制的仪器。然后，他将使用这个仪器将他目前的星系样本扩展到南半球。这个项目的更广泛的影响包括一个重要的教育组成部分。该研究员将为监狱教学倡议(PTI)开发和教授一门新课程。PTI计划在普林斯顿大学附近的两个青少年管教机构向囚犯教授大学学分课程。这些学生可以通过该项目获得两年制学位，获释后可以进入四年制大学。该课程将侧重于物理学和天文学，旨在发展解决问题的科学方法和欣赏科学在日常生活中的实际应用。大多数证据表明，改善监狱人口的教育是减少获释后重返犯罪的主要原因。这位学者将把他以前的教学技能和对科学的热情带给应得的、代表不足的人群。

Dr. Jeremy D. Murphy is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at Princeton University. The current cosmological paradigm includes a significant and unknown physical entity called "dark matter." While the presence of dark matter (DM) in galaxies is well established, the extent of galaxy DM halos and the role DM plays in galaxy formation and evolution is largely unknown. As the current cosmological paradigm governing the hierarchical clustering of DM halos makes specific predictions about their formation timescales and merger history, a clear understanding of the mass of DM halos on galaxy scales is needed. In this project the fellow will focus on directly constraining the mechanisms and timescales of elliptical galaxy formation. The recent discovery of quiescent, red elliptical galaxies at redshift around z~2 raises many questions regarding the Lambda Cold Dark Matter hierarchical picture of galaxy formation. Fortunately, galaxies leave both chemical and kinematic clues to their formation histories. Advances in integral field spectroscopy and dynamical modeling have begun to open the window into understanding the DM distribution, DM central density, the stellar orbital anisotropy and chemical abundance gradients of elliptical galaxies. In this project the fellow will continue his study of the formation and evolution of massive elliptical galaxies. Specifically, this project has the following aims: (1) The fellow will use 2D stellar kinematics from VIRUS-P and orbit-based, axisymmetric dynamical modeling to constrain the DM halo mass, the DM central density, the stellar orbital anisotropy and stellar abundance gradients. From this he will be able to place direct constraints on the timescales and possible mechanisms of galaxy formation. (2) The fellow will compare mass estimates based on stellar kinematics to other methods of estimating mass in galaxies in order to quantify any systematics between these different methods. (3) The fellow will bring his experience with the commissioning of the VIRUS-P spectrograph, and his detailed study of the instrument's fiber optics, in order to successfully install a duplicate instrument on the DuPont telescope at Las Campanas Observatory. He will then use this instrument to expand his current galaxy sample into the Southern Hemisphere.The broader impacts of this project include a significant educational component. The fellow will develop and teach a new course for the Prison Teaching Initiative (PTI). The PTI program teaches college-credit courses to inmates at two youth correctional facilities near Princeton University. The students can earn a two-year degree through the program and go onto four-year colleges upon release. The course will focus on physics and astronomy and aim to develop both a scientific approach to problem solving and an appreciation of the practical application of science in daily life. The large majority of evidence indicates that improving education in a prison population is the leading cause in reducing a return to crime upon release. The fellow will bring his previous teaching skills and enthusiasm for science to a deserving, underrepresented population.